The Plain Truth of the Scriptures?

Every once in a while I head on over to the blog of Craig Alan Myers on the Brethren Revival Fellowship sight to what's up with the BRF. This morning Craig had this quote from the famed 19th century British preacher Charles Spurgeon:

I am sometimes told by my people that I attack certain parties very hard. Well, I cannot help it; if they are not right, it is not my fault—if they come in my way, that I am compelled to run over them. Suppose two of you should be driving in the road to-morrow, and one of you should be on the right side of the road, and some accident should occur, you would say, "Sir, the other man ought to have pulled up, he must pay the damages, for he had no business there at all on his wrong side." And it will be the same with us if we preach God's truth; we must go straight on; if the greatest ill feeling in the world rise up we have nothing to do with it.
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No man has a right to believe what he likes; he is to believe what God tells him; and if he does not believe that though he is not responsible to man, or to any set of men, or to any government, yet mark you, he is responsible to God. I beseech you, therefore, if you would avoid heresies, and bring the church to a glorious union, read the Scriptures.

If you would avoid heresies... read the scriptures? Every "heretical" group is reading the scriptures. And why is it that there are hundreds if not thousands of denominations who each believes it is the one reading the scriptures correctly? Why isn't there just one church if the scriptures are so clear?